Split ammonia absorption system



Patented Feb. 21, 1950 SPLIT AMMONIA ABSORPTION SYSTEM Charles D.Hartman,'Jr., New York, and Almon J. Cordrey, Garden City, N. Y.

Application September 12, 1946, Serial No. 696,598

13 Claims.

it relates particularly to systems for heating railway cars or othermobile vehicles that are used for transporting perishable produce, suchas, vegetables, fruits and the like.

Refrigerator cars, when used for transporting perishable produce in thewintertime, may be subjected to such low temperatures that the producetherein may be damaged by freezing.

It has been proposed heretofore to provide heating systems which can beset into operation in order to protect the produce and retain it at asufliciently high temperature to prevent the produce from freezing. Suchheating devices may consist of coal, oilI or gas fired stoves, which, ofcourse, occupy space in such refrigerator cars. Inasmuch as the spaceavailable for loading the cars is limited, it is desirable to provide aheating system which doessnot occupy much space, and preferably no morespace than is normally occupied by the refrigerating means normallyprovided in such refrigerating cars. Moreover, such heating means shouldbe relatively fool proof and should be of such nature that ready controlthereof and minimum fire hazard are assured.

In accordance with the present invention, we have provided `heatingsystems for refrigerator cars and other mobile vehicles or chambers inwhich heat is generated by the exothermic reaction produced byabsorption of ammonia gas in weak aqua ammonia. The car may be heated bysupplying expanded ammonia gas,to a coil or heat exchanger whichcontains a dilute solution of aqua ammonia whereby the gas will be j`and further by controlling the rate at which they stronger aqua ammoniais discharged from the system, it is possible to heat the coils or heatexchangers in the car sufficiently to offset heat loss through ,thewalls of the car even at low temperatures, and thereby maintain atemperature in the refrigerator car sufciently high to preservefoodstuffs or other articles carried therein against freezing.

In a typical system, the refrigerator car or other vehicle may beprovided with a receiver for liquid ammonia at about the temperature onthe exterior of the car. This receiver and a second receiver for weakaqua ammonia preferably are placed on the exterior of the car. 'I'heammonia is allowed to expand through a coil and heat exchangerpreferably outside the car where it absorbs heat from the atmosphere,even though the atmosphere is at a very low temperature. This evaporatedor expanded ammonia and the weak aqua ammonia are supplied to a coil orheat exchanger within the refrigerating chamber where the ammonia goesinto a solution in the weak aqua ammonia thereby heating the coil. Asthe stronger solution is formed, it is allowed to escape from the coilafter giving oi some of this heat and may be delivered by the pressurein the system to a receiver, preferably also on the exterior of the car.By including a relief valve that permits the strong aqua ammonia toescape from the coil, the interior of the car may be maintained abovefreezing temperatures. The relief valve may suitably comprise anexpansion chamber having a float controlled valve' associated therewithwhich allows the strong aqua ammonia to escape from the coil after ithas travelled through the coil.

The system described generally above may be used for refrigerating theinterior of the car by reversing the cycle and utilizing the ammoniareceiver noted above for receiving ammonia for expansion into the coilsand utilizing the strong ammonia and weak aqua ammonia receivers asabsorbers for the expanded ammonia in the coil. Thus, by the provisionof suitable valves and connections between the receivers and the heatexchange coils, it is possible to use substantially the same system forheating and cooling the cars, thereby conserving space and simplifyingthe equipment required for heating and cooling the car.

For a better understanding of the present invention, reference may behad to the accompanying drawing in which the single figure is adiagrammatic illustration of a typical system for heating and coolingrefrigerating cars and other devices.

As indicated above, the heating system embodying the present inventionoperates on the principle that the absorption of ammonia gas in a weakaqua ammonia solution generates heat. The heating effect of such areaction may be taken advantage of in many different systems, such asthe system illustrated in the drawing. This system includes a first tankor receiver IU which is adapted to be charged with liquid ammonia andinasmuch as it may be disposed on the exterior of the chamber Il,illustrated in dotted lines, the ammonia will be at about thetemperature of the surrounding atmosphere. The

3 liquid ammonia may be supplied to the receiver Il at servicingstations located at suitable points along a railroad. The receiver IIImay be provided with a heat exchanger coil or surface I2 connected tothe top and bottom of the receiver where the ammonia may evaporate andabsorb heat from the atmosphere. The receiver I is connected by meansofa conduit I3 to an aspirator I4 which directs the gas into the heatingor cooling coil l5 within the chamber Il.

The conduit I3 is provided with a. thermostatically controlled valve I6which may be set to be open at temperatures below about 34, for example,and to be closed at temperatures above 34 so that the ammonia issupplied to the coll I5 when the temperature in the chamber approachesfreezing. The thermostatic valve preferably is an adjustable type withreversible connections so that it also can be adjusted to close at a lowtemperature and open at a higher temperature. The opposite end ofthecoil I5 from the aspirator I4 is connected to an expansion chamber I 'Iwhich is gas-tight and is provided with a float-controlled valve I8 ofconventional type. The valve I8 is adapted to open when the chamber Ilis about full and close when the liquid therein is discharged throughthe conduit I9. This conduit is connected to a receiver which collectsthe liquid from the float chamber I1 and coil I5 as it is discharged.

Weak aqua ammonia, for example, a 6% solution o! ammonia in water, forabsorbing the 'ammonia gas is supplied from a third receiver 2l alsomounted outside the chamber -I I. The weak aqua is maintained under apressure of about to 80 pounds per square inch by charging the receiverwith compressed air. The weak aqua ilows through a pressure reducingvalve 22 in the con- As the strong aqua tank is exposed to thetemperature of the outside atmosphere, which isat or below 30 F. whenheat is required inside the car, the pressure in the strong aqua tank20, connected to chamber I'I through conduit IS is at all times belowthe pressure in coil I5, and the strong aqua from coil I5 will flowthrough chamber Il into the receiver 2l by pressure dierential.

Under the conditions specified above, the temperature of the coil I5will be raised by the generation of heat of absorption suirlciently tomaintain the car above freezing temperature even when the outsidetemperature is as low as -20 F., assuming of course, that the car iswell insulated. Coil temperatures as high as 55 F. are easily attained.It will be understood that the operation of the system is not continuousfor the supply of ammonia gas will be shut oli' by the thermostaticvalve I6 when the temperature of the car is raised suiciently. Similarlythe supply of weak aqua will be shut oi by means of thethermostatically-controlled valve 25.

duit 23 into the 'aspirator I4 and mixes with the ammonia gas and ilowsthrough the coil I5. The rate of flow of weak aqua may be controlled bya restricted orlce 24 in the conduit 23. The oriilce 24 may be of adiameter, for example, to permit the weak aqua to be supplied at therate of about three gallons per minute to the coil I5. The conduit 23 isalso provided with a thermostatic valve 25 for shutting o the ow of weakaqua to the coil I5, when the temperature in the chamber exceeds apredetermined value, for example, 34" F. f

The above described system contains all the elements necessary forheating the car and operates as follows:

The ammonia in the receiver III, and in exchanger surface I2 expandsinto gas and passes through the conduit I3 into the coil I5 where itdissolves in the weak aqua ammonia supplied from the receiver 2l. As theammonia dissolves. it gives o heat at the rate of about 840 B. t. u.sper pound of ammonia. The specific gravity oi the liquid in the coil I5changes andthere is a tendency, of course, for the concentration of theliquid in the pipes to become equalized with the result that ow takesplace in the coil I5 toward the chamber I'I. This ow is also iniiuencedby the pressure of the ammonia gas and the iiow into coil I5of the weakaqua ammonia.

The oat valve I8 is utilized to discharge strong aqua from the coil,intermittently, when the mixture of NH3 gas and weak aqua havesufliciently increased the volume of the mixture in the coil to iill theexpansion chamber in the float valve body. When the float is raisedsuillciently the iloat valve opens and discharges the strong aquaammonia into the receiver 2li.

This system can be modified to permit it to be used for cooling carsduring the summer months. Essentially the changes-consist in theaddition of suitable valves and conduits for reversing the cycle ofoperation. Thus a manually operated valve 26 may be placedin the conduitI3, a valve 2l interposed between the coil I5 and the chamber I1, avalve 28 placed in the conduit 23 between the receiver 2l and thepressure reducing valve 22. A valve 29 isr placed in the conduit I9 anda conduit 3l having a valve 30' therein is provided for connecting thelreceivers 2B and 2l. Another conduit 32 is added to connect thereceiver 2i to thecoil I5 downstream of the aspirator I4. The vconduit32 may be provided with valves 33 and 34 at its opposite ends. Anotherconduit 35 is connected to the conduit I3 between the valves I6 and 26and to the remote end of the coil I5. A manually operated valve 36 and athermostatically controlled' thermal expansion valve 3l are interposedin the conduit For eiilcient operation of the cooling system it isnecessary to provide a suction pressure valve.

preferably thermostatically controlled, as dis` closed in the Cordreyapplication Ser. N o. 565,436, between the discharge end of an expansioncoil I5 and the ammonia absorber. In this system such a suction pressurevalve 38 is placed in the conduit 32 between the valves` 33 and 34. Theconduit 23 may be provided with another valve 39 near the aspirator I4.

The system described above and shown in the drawings may beused -forheating or for cooling. The system is conditioned for heating by openingthe valves 26, 2l, 28, 29 and 39 and closing the valves 30, 33, 34 and36 whereby the cycle of operation described above takes place.

To provide refrigeration with the system, the valves 26, 21, 28, 29 and39 are closed and the valves 30, 33, 34 and 36 are'opened. Thisadjustment of the valves causes the receiver I0 to be connected throughthe valve I5, conduit I3 and conduit 35 to the lower end of the coil I5.

The receivers 20 and 2| are connected to the' other end of the coilthrough the conduit 32. The float valve chamber and the conduit 23 aredisconnected from the fluid circuit. I

The receiver I0 is lled with liquid ammonia, preferably precooled orsubcooled and air pressure is applied to the liquid to force it into thecoil I5. The valve 36 may be used as a presaccesso sure reducing valveand the thermal expansion valve 31, as well as the thermostatic valveI6,

control the flow of the ammonia to the coil. The

thermostatic valve I6 may be adjusted to close at a predetermined lowtemperature, for example 38 F. The ammonia evaporates in the coil I5 andthe coil temperature is regulated by the suction pressure controll valve38 as described in application Ser. No. 565,436, the escaping gasiiowing to the receivers 2li and 2l which are illled with Weak aquaammonia for absorbing the ammonia gas.

From the preceding description, it will be apparent that We haveprovided a system which may be utilized either for heating or forcooling and which is automatic after it has been set into operation.

It will be understood that the arrangement of the system is susceptibleto considerable modification, particularly in the design of the coils,the receivers, the valves used therein and other details thereof.Therefore, the forms of the invention described herein should beconsidered as illustrative only.

We claim:

l. A heating system for a chamber comprising a rst heat exchange coilwithin said chamber, a second heat exchange coil outside of saidchamber, means for supplying strong ammonia to said second coil forexpansion therein and absorption of heat and then to said flrst coil,means for supplying weak aqua ammonia to said first coil to absorb saidstrong ammonia and thereby generate heat and form strong aqua ammonia insaid first coil, and means for collecting said strong aqua ammonia fromsaid iirst coil and discharging it intermittently.

2. A heating system for a. mobile vehicle comprising a coil Within saidvehicle, a reservoir for receiving ammonia under pressure carried bysaid vehicle, a receiver for weak aqu-a ammonia under pressure carriedby said vehicle, means connecting said reservoir and said receiver tosaid coil for supplying said coil with said weak aqua ammonia and saidammonia for absorption of said ammonia in said weak aqua ammonia toproduce strong aqua ammonia and heat, and means for receiving saidstrong aqua ammonia from said coil and discharging it intermittently.

3. A heating system for a mobile vehicle comprising a coil within saidvehicle, a reservoir for receiving ammonia carried by said vehicle, areceiver for weak aqua ammonia under pressure carried by said vehicle,means connecting said reservoir and said receiver to said coil forsupplying said coil with said weak aqua ammonia and said ammonia forabsorption of said ammonia in said weak aqua ammonia to produce strongaqua ammonia and heat, and means for receiving said strong aqua ammoniafrom said coil, and means intermediate said coil and said last-namedreceiving means for controlling the rate of discharge of said strongaqua ammonia from said coil.

4. A heating system for a chamber comprising a iirst heat exchange coilwithin said chamber, a second heat exchange coil outside of saidchamber, means for supplying ammonia to said second coil for evaporationtherein and absorption of heat and then to said first coil, means forsupplying weak aqua ammonia. to said first coil to absorb the ammoni-avapor and thereby produce strong aqua ammonia and generate heat in saidrst coil, means for receiving said strong aqua ammonia from said firstcoil, and means intermediate said coil and said last-named receivingmeans for controlling the iiow oi' said strong aqua ammonia from saidfirst coil to said receiving means.

A5. A heating system for a. refrigerating chamber comprising a heatexchanging coil in said chamber, means for supplying weak aqua ammoniato said coil, means for supplying ammonia vapor to said coil forabsorption in said aqua ammonia to form strong aqua ammonia and generateheat, an expansion chamber connected to said coil for receiving saidstrong aqua ammonia from said coil, a. float valve in said chamber fordischarging said strong aqua Iammonia from said chamber, and a. receiverfor said strong aqua ammonia connected to said chamber.

6. A heating system for a refrigerating chamber comprising a heatexchanging coil in said chamber, means for supplying weak aqua arnmoniaunder pressure to said coil, means for supplying ammonia vapor to saidcoil for absorption in said aqua ammonia to form strong aqua ammonia andgenerate heat, an expansion chamber connected to said coil forvreceiving said strong aqua ammonia from said coil, a float valve in saidchamber for discharging said strong aqua ammonia from said chamber, anda receiver for said strong aqua ammonia. connected to said chamber.

7. A heatingsystem for a refrigerating chamber comprising a heatexchanging coil in said chamber, a receiver for ammonia connected to oneend of said coil, a receiver for weak aqua ammonia under pressureconnected to said one end of said heat exchanging coil, means responsiveto the temperature of said chamber for controlling the flow of ammoniato said heat exchanging coil, means responsive to the temperature ofsaid chamber for controlling the flow of weak aqua ammonia to said heatexchanging coil, a closed expansion chamber connected to the other endof said heat exchanging coil, a receiver connected to said expansionchamber, and a float valve in said expansion chamber controlling flowfrom said expansion chamber to the last-mentioned receiver. f

8. A heating system for a refrigerating chamber comprising a heatexchanging coil in said cham-y ber, a receiver for ammonia connected toone end of said coil, a receiver for weakaqua ammonia under pressureconnected to said one end of said heat exchanging coil, means forcontrolling the rate of flow of weak aqua ammonia to said heatexchanging coil, means responsive to the temperature of said chamber forcontrolling the fiow of ammonia to said heat exchanging coil, meansresponsive to the temperature of said chamber for controlling the flowof weak' aqua ammonia to said heat exchanging coil, a closed expansionchamber connected to the other end of said heat exchanging coil, areceiver.' connected to said expansion chamber, and a float valve insaid expansion chamber controlling ilow from said expansion chamber tothe last-mentioned receiver.

` 9. A heating system for a refrigerating chamber comprising a heatexchanging coil in said chamber, a receiver for ammonia connected to oneend of said coil, an evaporatingcoil interposed between said receiverand said heat exchanging coil,` a receiver for weak aqua ammonia underpressure connected to said one end of said heat exchanging coil, meansresponsive to the temperature of said chamber for controlling the flowof ammonia to said heat exchanging coil, means responsive to thetemperature of said chamber for controlling the flow of weak aquaammonia to said chamber controlling flow from said expansion` chamber tothe last-mentioned receiver.

10. A heating system for a refrigerating chamber comprising a heatexchanging coil in said chamber, a receiver for ammonia connected to oneend of said coil, an evaporating coil interposed between said receiverand said heat exchanging coll, a receiver for weak aqua ammonia underpressure connected to said one end of said heat exchanging coil, meansfor` controlling the rate of flow of weak aqua ammonia to said heatexchanging coil, means responsive to the temperature of said chamber forcontrolling the ow of ammonia to said heat exchanging coil, meansresponsive to the temperature of said chamber for controlling the ow ofweak aqua ammonia to said heat exchanging coil, a closed expansionchamber connected to the other end of said heat exchanging coil, areceiver connected to said expansion chamber, and a oat valve in saidexpansion chamber controlling flow from said expansion chamber to thelast-mentioned receiver.

11. A heating and cooling system for a refrigsaid receiver and said coilfor connecting and disconnecting said receiver and said coil, a secondreceiver connected to said one end of said coil for suplying liquidunder pressure to said coil, means restricting the flow of liquid tosaid coil, a second thermostatically controlled valve between saidsecond receiver and said coil for connecting and disconnecting saidreceiver and said coil, a third receiver, an expansion chamberinterposed between and connected to the other end of said coil and saidthird receiver, and a float-controlled valve in said expansion chamberfor controlling iiow from said expansion chamber to said third receiver.

12. A heating and cooling system for a refrigerating chamber comprisinga heat exchanging coil in said chamber, a'receiver connected to one endof said coil for supplying vapor to said coil, a first thermostaticallycontrolled valve between said receiver and said coil for connecting anddisconnecting said receiver and said coil, a second receiver connectedto said one end of said coil for supplying liquid under pressure to saidcoil, means restricting the flow of liquid to said coil, a secondthermostatically controlled valve between said second receiver and saidcoil for connecting and disconnecting said receiver and said receiver, afirst connection from said one end of said coil to said second and thirdreceivers, a suction pressure control valve in said connection, a secondconnection interposed between said rst thermostatically controlled valveand said other end of said coil, a thermal expansion valve in saidsecond connection, and means for selectively re,- versing connectionsbetween said receivers and said coil, and connecting and disconnectingsaid expansion chamber for selectively heating and cooling said coil.

' 13. A heating and cooling system for a refrigerating chamber, a heatexchanging coil, a iirst receiver, a first connection between said firstreceiver and one end of said coil, a thermostatically controlled valveresponsive tothe temperature of said chamber in said connection, asecond connection between said receiver and the other end oi said coil,a tlzermal expansion valve in said second connection, a second receiver,i'st means connecting said second receiver to said one end of I saidcoil, a flow control valve and a thermostatically controhed valveresponsive to the temperature of said chamber in said i'lrst connectingVmeans, a third receiver, an expansion chamber means connecting saidother end of said coil, said expansion chamber and said third receiverin series, a naat-controlled valve in said expansion chamber forconnecting and disconnecting said third receiver and said expansionchamber, a third connection between said one end of said coil and saidsecond and third receivers, a suction pressure control valve in saidthird connection, and manually controlled valves in said connections andconnecting means for reversing the connections between said receiversand coil to selectively heat and cool said refrigerating chamber.

CHARLES D. HARTMAN, JR. ALMON J. CORDREY.

REFERENCES CITED The following references are of record in the lc ofthis patent:

UNITED STATES PATENTS Number Name Date 444,532 Holden Jan. 13, 18912,064,040 Smith Dec. 15, 1936 2,374,972 Biehl May 1, 1945

